Purification method of strontium

Abstract

The invention relates to a strontium purification method which comprises the following steps: filling cation exchange resin into a column to obtain an adsorption column and a displacement column, respectively transforming the cation exchange resin in the adsorption column and the displacement column into sodium resin and calcium resin to correspondingly obtain a sodium adsorption column and a calcium displacement column, and purifying the sodium adsorption column and the calcium displacement column to obtain strontium. The method comprises the following steps of: adsorbing strontium-containing feed liquid by using a sodium type adsorption column, firstly connecting a calcium type displacement column behind the sodium type adsorption column, adding a displacement agent, then connecting an additional calcium type displacement column, and adding displacement agents with different acidity before and after the calcium type displacement column to perform displacement separation on strontium. Compared with the prior art, the method realizes effective separation of strontium.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of spent fuel reprocessing, and relates to a strontium purification method. BACKGROUND

[0002] After uranium and plutonium are separated from spent fuel through the PUREX process, a waste liquid containing high radioactivity and high acidity is generated. In addition to residual uranium, plutonium, minor actinide elements, lanthanide elements, the waste liquid also contains a large amount of fission fragment elements such as strontium, cesium, ruthenium, rhodium, palladium, molybdenum, zirconium, iron, etc. Strontium has important applications in the fields of medicine, energy, etc. As an important isotope of strontium, strontium-90 is a high heat release nuclide with a half-life of 28.79 years, and is a pure beta emitter with high energy. It can not only be used as a heat conversion form of nuclear battery energy source, but also has a relatively wide use in the fields of clinical medicine, industrial process control, heat source of special equipment, instrument calibration reference source, etc. In addition, the separation and extraction of strontium reduce the radioactivity of high-level waste liquid and the difficulty of subsequent treatment and disposal.

[0003] Calcium, strontium and barium belong to the same main group elements, and their chemical properties are extremely similar. Liquid-liquid extraction process cannot effectively separate strontium and calcium, etc. Therefore, a large amount of calcium, a small amount of barium and other impurities are still contained in the crude product after liquid-liquid extraction, and thus further separation and purification is required to meet the product purity requirements. At present, there is no simple method that can better separate strontium.

[0004] Patent CN117899656A discloses a purification method for extracting strontium-89 from a reactor using uranyl nitrate solution as nuclear fuel. The strontium-89-containing deposit in the rear section of the reactor gas bypass is eluted with dilute nitric acid to obtain solution 1. A zirconium phosphate ion exchange column is used to adsorb solution 1, and after adsorption is completed, a nitric acid solution is used for elution to collect the adsorption effluent and elution liquid to obtain solution 2. A first cation exchange resin column is used to adsorb solution 2, and then a hydrochloric acid solution is used for desorption to obtain solution 3. A second cation exchange resin column is used to adsorb solution 3, and then an ammonium acetate solution is used for desorption to obtain solution 4. Sodium hydroxide solution is added to solution 4 and evaporated to remove ammonium ions, then concentrated hydrochloric acid is added and evaporated to remove acetate ions, then concentrated hydrochloric acid is added to dissolve the residue and sodium hydroxide solution is added to adjust the pH value to neutral. A strontium chloride [Sr] solution product meeting the medical requirements is obtained. 89 However, the patent uses hydrochloric acid and ammonium acetate for desorption, and then uses sodium hydroxide and hydrochloric acid to remove the newly introduced ammonium and acetate, respectively, which is a complex process.

[0005] Patent CN1087687A discloses a process for purifying copper electrolyte. The process involves contacting the copper electrolyte containing 50-250 g / L sulfuric acid with a chelating cation exchange resin to adsorb antimony and bismuth. Then, an aqueous solution containing 1-10 g / L alkali metal hydroxide and 2-60 g / L disodium ethylenediaminetetraacetate is used as the eluent to remove the antimony and bismuth from the resin. However, this patent uses alkali metal hydroxide and disodium ethylenediaminetetraacetate as the binding eluent, resulting in complex material usage and introducing new cations that need to be removed. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the existing technologies, such as the inability of commonly used chemical and physical methods to effectively separate and purify calcium, strontium, and barium, and to provide a method for strontium purification. This invention achieves effective separation of strontium.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] One of the technical solutions of the present invention is to provide a method for purifying strontium, the method comprising the following steps:

[0009] Cation exchange resin was packed into columns to obtain adsorption columns and substitution columns. The cation exchange resins in the adsorption and substitution columns were then converted into sodium (Na) type resin and calcium (Ca) type resin, respectively, to obtain sodium type adsorption columns and calcium type substitution columns. Sodium type adsorption columns were used to adsorb strontium-containing feed solutions. After sodium type adsorption columns, calcium type substitution columns were first connected and substitution agents were added. Then, additional calcium type substitution columns were connected and substitution agents with different acidities were added before and after the columns to perform substitution separation of strontium.

[0010] Furthermore, the cation exchange resin is a type 732 cation exchange resin, and the substitution agent is ethylenediaminetetraacetic acid (EDTA).

[0011] Furthermore, the feed solution contains cesium (Cs), calcium, strontium (Sr), barium (Ba), and lanthanum (La), with the concentration of each metal cation being 20~500 mg / L, and the acidity of the feed solution being pH=3~5.

[0012] As a preferred technical solution, the concentration of cesium in the feed solution is 20~25 mg / L, the concentration of calcium is 90~110 mg / L, the concentration of strontium is 400~500 mg / L, the concentration of barium is 40~60 mg / L, and the concentration of lanthanum is 40~60 mg / L.

[0013] As a preferred technical solution, the acidity of the feed solution is adjusted using an acid solution, wherein the acid solution is nitric acid (HNO3) and the concentration of the acid solution is 2~3 mol / L. If the acidity of the feed solution is adjusted too much, an alkaline solution is used to adjust it again, wherein the alkaline solution is sodium hydroxide (NaOH) solution and the concentration of the alkaline solution is 0.1~1 mol / L.

[0014] As a preferred technical solution, wet packing is used to minimize air bubbles and gaps in the column.

[0015] Furthermore, the column height, resin mass, and liquid volume of the packed column are (30~70 cm):(180~220 g):(5~10 L).

[0016] Further, the cation exchange resin in the adsorption column and the displacement column is washed with water until the washing effluent becomes clear.

[0017] The cation exchange resin in the adsorption column and the displacement column is converted to hydrogen form resin using acid solution and acid-soluble impurities are removed. The hydrogen form resin is then washed with water.

[0018] The hydrogen form resin in the adsorption column is converted to sodium form resin using a sodium salt solution to obtain a sodium form adsorption column. The sodium form resin is then washed with water.

[0019] The hydrogen form resin in the substitution column is converted to the calcium form resin using a calcium salt solution to obtain a calcium substitution column. The calcium form resin is then washed with water.

[0020] After the transformation, the resin is washed with water to remove the remaining impurity solution in the column.

[0021] Furthermore, the cation exchange resin in the adsorption column and the displacement column is washed with water at a flow rate of 2-5 L / h for 1-2 h.

[0022] The flow rate of acid solution used to convert the cation exchange resin in the adsorption column and the displacement column to the hydrogen form resin is 2-5 L / h, and the time is 2-5 h. The acid solution used is nitric acid, and the concentration of the acid solution is 2-3 mol / L. The flow rate of water used to wash the hydrogen form resin is 2-5 L / h, and the time is 10-30 min.

[0023] The flow rate of the sodium salt solution used to convert the hydrogen form resin in the adsorption column to the sodium form resin is 2-5 L / h, and the time is 2-5 h. The sodium salt used is sodium nitrate (NaNO3), and the concentration of the sodium salt solution is 1-3 mol / L. The flow rate of the water used to wash the sodium form resin is 2-5 L / h, and the time is 10-30 min.

[0024] The flow rate for converting the hydrogen-form resin in the displacement column to the calcium-form resin using a calcium salt solution is 2-5 L / h, and the time is 2-5 h. The calcium salt used is calcium nitrate (Ca(NO3)2), and the concentration of the calcium salt solution is 1-3 mol / L. The flow rate for washing the calcium-form resin with water is 2-5 L / h, and the time is 10-30 min.

[0025] Furthermore, the feed solution is introduced into the sodium adsorption column for adsorption. The adsorbed effluent in the early stage is discharged into the waste liquid storage bottle and monitored in real time. Adsorption is stopped when strontium flows out from the lower outlet of the sodium adsorption column or when all the feed solution is adsorbed.

[0026] Wash the sodium adsorption column with water until no sodium is detected at the lower outlet of the sodium adsorption column, then stop washing.

[0027] As a preferred technical solution, sampling and analysis are performed every 5 to 10 minutes.

[0028] Furthermore, the flow rate of the feed solution introduced into the sodium adsorption column for adsorption is 2~5 L / h;

[0029] The sodium adsorption column is washed with water at a flow rate of 2-5 L / h for 30-60 min.

[0030] Furthermore, the sodium adsorption column and the calcium displacement column are connected, and the displacement agent solution is introduced into the sodium adsorption column for the first displacement to remove calcium. The effluent from the initial displacement is discharged into a waste liquid storage bottle and monitored in real time. The first displacement is stopped when the calcium concentration in the effluent at the lower end of the calcium displacement column is very low or when strontium flows out from the lower outlet.

[0031] Connect the sodium adsorption column, the calcium substitution column, and an additional calcium substitution column. First, introduce the substitution agent solution into the sodium adsorption column for a second substitution. During this process, strontium will be gradually carried by the substitution liquid from the sodium adsorption column and the calcium substitution column into the additional calcium substitution column. The initial effluent from the substitution is discharged into a waste liquid storage bottle and monitored in real time. When the calcium concentration in the effluent at the bottom of the additional calcium substitution column is very low or strontium flows out from the bottom outlet, the discharge is stopped.

[0032] Another low-acidity replacement agent solution is introduced into the sodium adsorption column for a second replacement. The product liquid effluent is collected and monitored in real time. When no strontium is detected at the lower outlet of the additional calcium replacement column, the second replacement is stopped. The strontium received in the strontium product storage bottle at this time is the purified strontium product.

[0033] As a preferred technical solution, sampling and analysis are performed every 5 to 10 minutes.

[0034] Furthermore, the flow rate of the excretory agent solution introduced into the sodium adsorption column for the first excretion is 2-5 L / h, the concentration of the excretory agent solution is 0.02-0.03 mol / L, and the acidity is pH=4.5-5.5;

[0035] The flow rate of the first step of introducing the excretory agent solution into the sodium adsorption column for the second excretion is 2-5 L / h. The concentration of the excretory agent solution is 0.02-0.03 mol / L, and the acidity is pH=4.5-5.5.

[0036] Then, another low-acidity replacement agent solution is introduced into the sodium adsorption column for a second replacement at a flow rate of 2-5 L / h. The concentration of the other low-acidity replacement agent solution is 0.02-0.03 mol / L, and the acidity is pH=6-7.

[0037] As a preferred technical solution, when introducing the excretory agent solution into the sodium adsorption column for the first excretion, the acidity of the excretory agent solution is adjusted with an alkaline solution, wherein the alkaline solution is a sodium hydroxide solution with a concentration of 5-8 mol / L. If the acidity of the excretory agent solution is adjusted too much, it is adjusted again with an acid solution, wherein the acid solution is nitric acid with a concentration of 2-3 mol / L.

[0038] When the replacement agent solution is first introduced into the sodium adsorption column for the second replacement, the acidity of the replacement agent solution is adjusted with an alkaline solution, wherein the alkaline solution is sodium hydroxide solution with a concentration of 5-8 mol / L. If the acidity of the replacement agent solution is adjusted too much, it is adjusted again with an acid solution, wherein the acid solution is nitric acid with a concentration of 2-3 mol / L.

[0039] When another low-acidity replacement agent solution is introduced into the sodium adsorption column for a second replacement, the acidity of the replacement agent solution is adjusted using an alkaline solution, wherein the alkaline solution is sodium hydroxide solution with a concentration of 5-8 mol / L. If the acidity of the replacement agent solution is over-adjusted, it is adjusted again using an acid solution, wherein the acid solution is nitric acid with a concentration of 2-3 mol / L.

[0040] One of the technical solutions of the present invention is to provide a product obtained by the purification method of strontium described above.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] (1) The present invention uses the ion exchange substitution method, which utilizes the adsorption capacity of cation exchange resin for cations such as cesium, calcium, strontium, barium, and lanthanum, and the difference in the force of substitution agent on these cations. After adsorption by sodium adsorption column, the first substitution by sodium adsorption column and calcium substitution column, and the second substitution by substitution agent solutions of different acidities on sodium adsorption column and two calcium substitution columns, strontium in the feed solution can be successfully separated from divalent cations such as calcium and barium, as well as monovalent and trivalent cations such as cesium and lanthanum, thereby achieving the effect of complete separation of strontium and obtaining a strontium solution product with high purity.

[0043] (2) In this invention, when the sodium adsorption column is used for adsorption, the cation exchange resin has a greater adsorption and binding capacity for high-valent cations than for low-valent cations. Monovalent cations are not easily adsorbed onto the cation exchange resin for separation. When the calcium-type substitution column is used for substitution by the substitution agent solution, the high-valent cations are first separated by the greater adsorption and binding capacity of the substitution agent solution for high-valent cations than for low-valent cations. Trivalent cations are easily bound onto the substitution agent for separation. Then, the calcium ions are released first by the strong adsorption and binding capacity of the high-acidity substitution agent solution. The strontium ions are released and collected by the strong adsorption and binding capacity of the low-acidity substitution agent solution. Finally, barium ions are collected.

[0044] (3) The method of the present invention is simple to operate, convenient and feasible, and meets the requirements for the separation and purification of strontium in the feed liquid. It has broad application prospects in the field of strontium separation and recovery. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the first explantation process of the strontium purification method in an embodiment of the present invention;

[0046] Figure 2 This is a schematic diagram of the second permutation process of the strontium purification method in an embodiment of the present invention. Detailed Implementation

[0047] The present invention will now be described in detail with reference to specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0048] Unless otherwise specified, the equipment used in the following embodiments is conventional equipment in the art; unless otherwise specified, the reagents used are commercially available products or prepared by conventional methods in the art. In the following embodiments, unless otherwise described in detail, conventional experimental methods in the art can be used.

[0049] Unless otherwise specified, the following procedures are generally performed at room temperature and atmospheric pressure.

[0050] The real-time monitoring described below uses inductively coupled plasma optical emission spectroscopy (ICP-OES) testing.

[0051] Example:

[0052] A method for purifying strontium, the specific steps of which are as follows:

[0053] S1, Installing the column,

[0054] Three cation exchange resins, each 50 cm high, were prepared by wet packing: one adsorption column and two displacement columns. The goal was to ensure that the columns were free of air bubbles and gaps.

[0055] S2, Resin washing and transformation,

[0056] S2.1 Washing: Deionized water is introduced from the top of one adsorption column and two displacement columns at a flow rate of 3.5 L / h using a peristaltic pump to wash the 732 cation exchange resin until the wash effluent becomes clear, which takes 1.5 h.

[0057] S2.2, Acid washing and first transformation: 2.5 mol / L nitric acid (HNO3) was introduced from the top of one adsorption column and two displacement columns by a peristaltic pump at a flow rate of 3.5 L / h to perform the first transformation, transforming the 732 type cation exchange resin into hydrogen (H) form resin for 3.5 h and removing acid-soluble impurities. Then, deionized water was introduced from the top of the adsorption column and displacement column by a peristaltic pump at a flow rate of 3.5 L / h to wash the hydrogen form resin for 20 min and remove the remaining impurity solution in the column.

[0058] S2.3 Second transformation: A 2 mol / L sodium nitrate (NaNO3) aqueous solution was introduced from the top of an adsorption column using a peristaltic pump at a flow rate of 3.5 L / h to perform a second transformation, converting the hydrogen form resin to the sodium (Na) form resin for 3.5 h to obtain a sodium form adsorption column. Then, deionized water was introduced from the top of the sodium form adsorption column using a peristaltic pump at a flow rate of 3.5 L / h to wash the sodium form resin for 20 min to remove the remaining impurity solution in the column.

[0059] A 2 mol / L calcium nitrate (Ca(NO3)2) aqueous solution was introduced from the top of the two substitution columns using a peristaltic pump at a flow rate of 3.5 L / h for a second conversion, converting the hydrogen form resin to the calcium (Ca) form resin for 3.5 h to obtain a calcium-form substitution column. Then, deionized water was introduced from the top of the calcium-form substitution column using a peristaltic pump at a flow rate of 3.5 L / h for washing, washing the calcium-form resin for 20 min to remove the remaining impurity solution in the column.

[0060] S3, adsorption of the feed liquid by the sodium-type adsorption column.

[0061] S3.1 Preparation of crude strontium simulating feed solution: Based on the actual adsorption capacity of the resin, cesium nitrate (Cs NO3), calcium nitrate, strontium nitrate (Sr(NO3)2), barium nitrate (Ba(NO3)2), and lanthanum nitrate (La(NO3)3) were added to ultrapure water to prepare 7.5 L of crude strontium simulating feed solution. The concentration of cesium (Cs) in the feed solution was 22.5 mg / L, the concentration of calcium was 100 mg / L, the concentration of strontium (Sr) was 450 mg / L, the concentration of barium (Ba) was 50 mg / L, and the concentration of lanthanum (La) was 50 mg / L. The acidity of the feed solution was adjusted to pH=4 using 2.5 mol / L nitric acid. If the acidity was over-adjusted, it was readjusted again using 0.5 mol / L sodium hydroxide (NaOH) aqueous solution.

[0062] S3.2 Adsorption: Add the feed solution to the reagent bottle, and introduce the feed solution from the top of a sodium adsorption column using a peristaltic pump at a flow rate of 3.5 L / h. The initial adsorption effluent does not contain Sr. 2+ It contains a large amount of Na + A small amount of Cs + Therefore, it is directly discharged into the waste liquid storage bottle, monitored in real time, and sampled and analyzed every 5 minutes. Adsorption is stopped when strontium flows out of the lower outlet of the sodium adsorption column or when all the liquid is adsorbed.

[0063] S3.3, Water washing: Deionized water is introduced from the top of the sodium adsorption column using a peristaltic pump at a flow rate of 3.5 L / h for washing until the washing effluent is free of Na. + and Cs + Stop washing when the time is 45 minutes.

[0064] S4, calcium-type displacement column for displacing feed solution.

[0065] S4.1 First substitution: Connect one sodium adsorption column to the first calcium substitution column, with the two columns in series. Then, introduce a 0.025 mol / L EDTA aqueous solution with an acidity of pH=5 (adjusted with 6.5 mol / L sodium hydroxide solution; if the acidity is too high, readjust with 2.5 mol / L nitric acid) from the top of the sodium adsorption column using a peristaltic pump at a flow rate of 3.5 L / h to perform the first substitution, thereby achieving Ca... 2+ Removal, such as Figure 1 As shown, the effluent from the initial stage of displacement did not contain Sr. 2+ It contains a large amount of La 3+ and Ca 2+ Small amount of Na +and Cs + Therefore, it is directly discharged into the waste liquid storage bottle and monitored in real time. Sampling and analysis are performed every 5 minutes. The first substitution is stopped when the calcium concentration in the effluent at the bottom of the first calcium substitution column is very low or when strontium flows out from the bottom outlet.

[0066] S4.2 Second substitution: Connect one sodium adsorption column, the first calcium substitution column, and the second calcium substitution column. At this point, the three columns are in series. Then, introduce a 0.025 mol / L ethylenediaminetetraacetic acid (EDTA) aqueous solution with a pH of 5 (adjusted using a 6.5 mol / L sodium hydroxide solution; if the pH is too high, readjust again using 2.5 mol / L nitric acid) through a peristaltic pump at a flow rate of 3.5 L / h from the top of the sodium adsorption column for the second substitution. During this process, strontium will gradually be carried by the substitution solution from one sodium adsorption column and the first calcium substitution column into the second calcium substitution column. Figure 2 As shown, the effluent from the initial stage of displacement did not contain Sr. 2+ It contains a large amount of Ca 2+ Small amount of Na + and Cs + Therefore, it is directly discharged into the waste liquid storage bottle and monitored in real time. Sampling and analysis are performed every 5 minutes. When the calcium concentration in the effluent at the bottom of the second calcium-type displacement column is very low or strontium flows out from the bottom outlet, the waste liquid storage bottle is closed.

[0067] Then, an ethylenediaminetetraacetic acid (EDTA) aqueous solution with a concentration of 0.025 mol / L and an acidity of pH 6.5 (adjusted with 6.5 mol / L sodium hydroxide solution; if the acidity was over-adjusted, it was readjusted again with 2.5 mol / L nitric acid) was introduced from the top of the sodium adsorption column using a peristaltic pump at a flow rate of 3.5 L / h to continue the second displacement process. The strontium product solution storage bottle was opened to allow the Sr-containing solution to be exposed. 2+ The effluent from the second calcium-type substitution column flows into a temporary storage bottle for the strontium product. The process is monitored in real time, with samples taken and analyzed every 5 minutes. The second substitution is stopped when no strontium is detected at the lower outlet of the second calcium-type substitution column. The strontium received in the temporary storage bottle at this point is the purified strontium product.

[0068] When the total recovery rate of strontium is 96.99%, the purity of strontium in the strontium product solution can reach 98.9%; when the total recovery rate of strontium is 90%, the purity of strontium in the strontium product solution can reach 99.5%.

[0069] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for purifying strontium, characterized in that, The method includes the following steps: Cation exchange resin was packed into columns to obtain adsorption columns and substitution columns. The cation exchange resins in the adsorption columns and substitution columns were then converted into sodium-form resin and calcium-form resin, respectively, to obtain sodium-form adsorption columns and calcium-form substitution columns. The sodium-form adsorption column was used to adsorb the feed solution containing strontium. After the sodium-form adsorption column, a calcium-form substitution column was first connected and a substitution agent was added. Then, an additional calcium-form substitution column was connected and substitution agents with different acidities were added before and after to perform substitution separation of strontium.

2. The method for purifying strontium according to claim 1, characterized in that, The cation exchange resin used is type 732 cation exchange resin, and the substitution agent used is ethylenediaminetetraacetic acid.

3. The method for purifying strontium according to claim 1, characterized in that, The feed solution contains cesium, calcium, strontium, barium, and lanthanum, with the concentration of each metal cation ranging from 20 to 500 mg / L, and the acidity of the feed solution is pH 3 to 5.

4. The method for purifying strontium according to claim 1, characterized in that, The column height, resin mass, and liquid volume of the packed column are (30~70 cm):(180~220 g):(5~10 L).

5. The method for purifying strontium according to claim 1, characterized in that, The cation exchange resin in the adsorption column and the displacement column is washed with water. The cation exchange resin in the adsorption column and the displacement column is converted to hydrogen form resin using acid, and the hydrogen form resin is washed with water. The hydrogen form resin in the adsorption column is converted to sodium form resin using a sodium salt solution to obtain a sodium form adsorption column. The sodium form resin is then washed with water. The hydrogen form resin in the substitution column is converted to the calcium form resin using a calcium salt solution to obtain a calcium substitution column. The calcium form resin is then washed with water.

6. The method for purifying strontium according to claim 5, characterized in that, The flow rate of water used to wash the cation exchange resin in the adsorption column and the displacement column is 2~5 L / h, and the time is 1~2 h. The flow rate of acid solution used to convert the cation exchange resin in the adsorption column and the displacement column to the hydrogen form resin is 2-5 L / h, and the time is 2-5 h. The acid solution used is nitric acid, and the concentration of the acid solution is 2-3 mol / L. The hydrogen form resin is washed with water at a flow rate of 2-5 L / h for 10-30 min. The flow rate of the sodium salt solution used to convert the hydrogen form resin in the adsorption column to the sodium form resin is 2-5 L / h, and the time is 2-5 h. The sodium salt used is sodium nitrate, and the concentration of the sodium salt solution is 1-3 mol / L. The flow rate of the water used to wash the sodium form resin is 2-5 L / h, and the time is 10-30 min. The flow rate of calcium salt solution used to convert the hydrogen form resin in the displacement column to the calcium form resin is 2-5 L / h, and the time is 2-5 h. The calcium salt used is calcium nitrate, and the concentration of the calcium salt solution is 1-3 mol / L. The flow rate of water used to wash the calcium form resin is 2-5 L / h, and the time is 10-30 min.

7. The method for purifying strontium according to claim 1, characterized in that, The feed solution is introduced into the sodium adsorption column for adsorption. Adsorption is stopped when strontium flows out of the lower outlet of the sodium adsorption column or when all the feed solution is adsorbed. The sodium-type adsorption column was washed with water.

8. The method for purifying strontium according to claim 7, characterized in that, The flow rate for introducing the feed solution into the sodium adsorption column for adsorption is 2~5 L / h; The sodium adsorption column is washed with water at a flow rate of 2-5 L / h for 30-60 min.

9. The method for purifying strontium according to claim 1, characterized in that, Connect the sodium adsorption column and the calcium substitution column, introduce the substitution agent solution into the sodium adsorption column for the first substitution, and stop the first substitution when the calcium concentration in the effluent at the lower end of the calcium substitution column is low or strontium flows out from the lower outlet. Connect the sodium adsorption column, the calcium substitution column, and the additional calcium substitution column. First, introduce the substitution agent solution into the sodium adsorption column for a second substitution. When the calcium concentration in the effluent at the lower end of the additional calcium substitution column is low or strontium flows out from the lower outlet, stop the effluent. Another low-acidity replacement agent solution is introduced into the sodium adsorption column to continue the second replacement. The product liquid effluent from the replacement is collected. The second replacement is stopped when no strontium is detected at the lower outlet of the additional calcium replacement column.

10. A method for purifying strontium according to claim 9, characterized in that, The flow rate for introducing the excretory agent solution into the sodium adsorption column for the first excretion is 2-5 L / h, the concentration of the excretory agent solution is 0.02-0.03 mol / L, and the acidity is pH=4.5-5.5; The flow rate of the first step of introducing the excretory agent solution into the sodium adsorption column for the second excretion is 2-5 L / h. The concentration of the excretory agent solution is 0.02-0.03 mol / L, and the acidity is pH=4.5-5.

5. Then, another low-acidity replacement agent solution is introduced into the sodium adsorption column for a second replacement at a flow rate of 2-5 L / h. The concentration of the other low-acidity replacement agent solution is 0.02-0.03 mol / L, and the acidity is pH 6-7.

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